NASA’s future exploration of ocean worlds is enabled by Hubble’s monitoring of Europa’s putative plume activity and Cassini’s long-term investigation of the Enceladus plume. In particular, both investigations are laying the groundwork for NASA’s Europa Clipper mission, which is planned for launch in the 2020s.

The new findings are an independent line of evidence that hydrothermal activity is taking place in the Enceladus ocean. Previous results, published in March 2015, suggested hot water is interacting with rock beneath the sea; the new findings support that conclusion and add that the rock appears to be reacting chemically to produce the hydrogen.